We do not want Lino.run_row_action to add the parameter values of
its requesting panel when it is being run from within a “non-main
context”. A “non-main context” is currently only in
lino.core.actors.Actor.slave_as_html_meth() (i.e. when
slave_grid_format
is html. We now have a new attribute
lino.core.requests.BaseRequest.is_on_main_actor per request.

Note that currently we also don’t pass the mk and mt paramneters
(master key and master type). I think that this is correct.

But all this is to be observed.

Later I tried whether this fixes #1989. But it didn’t. I
continued to search.